Damage to the guided-missile destroyer USS Fitzgerald is seen as the vessel is berthed at its mother port in Yokosuka, southwest of Tokyo, on June 18. (Kazuhiro Nogi/AFP via Getty Images)

Ten years ago, Scott Cheney-Peters stood watch on the bridge of the USS Fitzgerald, a guided-missile destroyer deployed to the Pacific. Despite sophisticated navigation systems, keeping the ship a safe distance from other vessels in crowded maritime corridors was complex, especially at night, he said.

“The bridge teams have help from some automated systems that suggest what they think is happening and can alert the human operators to potentially dangerous situations,” said Cheney-Peters, the founder of the Center for International Maritime Security, which facilitates discussion of naval issues. “But as with any algorithm, those alerts can be occasionally thrown off, in this case by things like large waves or two other ships very close together — so it’s humans that have to ultimately make navigation decisions.”

Early Saturday morning, the Fitzgerald found itself at the center of one of the ugliest maritime incidents in years for the Navy. The 505-foot long ship collided off the coast of Japan with the Philippine-flagged MV ACX Crystal, a 730-foot container ship. The Crystal ripped a 12-foot hole in the starboard (right) side of the Fitzgerald’s hull, fully flooding the third and fourth platform levels of the ship and drowning seven sailors in sleeping quarters, according to Navy officials and an unclassified document obtained by The Washington Post.

The damage to the Fitzgerald, which typically carries about 279 U.S. service members, is so extensive that senior Navy officials are discussing spending $8 million to put it on a powerful heavy-lift ship and bring it back to a shipyard for repairs, the document said. The Navy did the same with the USS Cole, which was hit by terrorists with explosives in October 2000, and the USS Samuel B. Roberts, which was nearly sunk by an Iranian mine in the Persian Gulf in 1988.

Several investigations are now underway to determine what happened. And if past is prologue, the Navy will assess how human error on the part of either crew could have led to such a catastrophe, despite all of the radar and communication systems on board. Similar situations occur about once every decade or so, and are a “deep, powerful reminder of how fundamentally dangerous it is to operate warships at sea,” said retired Navy Adm. James Stavridis, who was once the captain of a sister destroyer, the USS Barry.

“To understand ‘how could this happen,’ you need to think of that particular area of the sea as an eight-lane highway, at night, with ships moving at speed — but no traffic lanes,” Stavridis said in an email. “Any sudden, erratic move by another ship poses an extreme risk, with little time to react, exactly as if a car just ahead of you on the highway suddenly turned around. At night, it’s hard to figure out the visual picture and correlate it with the radar images. The investigation will pull that apart with extreme diligence, and accountability will be swift and ruthless.”

Stavridis, now the dean of the Fletcher School of Law and Diplomacy at Tufts University, called the situation “heartbreaking,” and credited sailors on the Fitzgerald with saving the ship from sinking, which almost certainly would have made the loss of life far heavier.

“The incident will become the basis for extensive scenario training by the Navy to try as much as we can to avoid the next such incident — [everything] from ship handling, to command and control, to technology and warning systems will be examined and improved,” he said. “But the cost of losing those seven sailors will never be recovered, tragically. It is a heartbreaking day for the good ship Fitzgerald and her captain.”

Seven U.S. sailors went missing after a U.S. Navy destroyer collided with a Philippine-flagged merchant ship off the coast of Japan on June 17. A number of the missing sailors were found dead in the destroyer's flooded berthing compartments. (Elyse Samuels,Monica Akhtar/The Washington Post)

Previous collisions also may come up as the service scrutinizes how to avoid another accident. In one recent incident, the USS Porter, another destroyer, collided in 2012 in the Strait of Hormuz off the coast of Iran with the MV Otowasan, an oil tanker. An investigation found that the Porter’s crew missed that the tanker was in front of them while watching out for other traffic in the tightly congested waterway. In that case, the Porter’s captain, attempted to cross left ahead of the tanker to avoid a head-on collision, but was not able to do so in time to avoid a blow to the starboard side.

Analysts have so far questioned the unusual path of the Crystal, which was proceeding on a course toward Tokyo but performed a sudden U-turn and returned to where it had been. Company officials said the turn actually happened about an hour after the collision, as its crew turned back to check on the Fitzgerald.

One former naval surface warfare officer, speaking on the condition of anonymity because of the sensitivity of the situation, said it appeared to him that the Fitzgerald was in the wrong when it was struck by the Crystal.

“I’m always troubled when you see a hit on the [right] side,” the former Navy officer said. “My gut is that [the captain] will be questioned on why he didn’t turn right.”

The officer said he was surprised that Benson wasn’t on the bridge at the time of the collision, and was instead hurt in his quarters. The waterways where the two vessels collided are notorious for the heavy volume of shipping traffic, where lights and radars contacts can make navigation extremely difficult.

After seeing where the collision was, the officer said those with experience in damage control knew right away what had become of the missing sailors, as their berthing areas flooded and were sealed.

“We knew they were trapped inside,” he said. “We knew it had turned into a chamber of death.”

Among the work the Navy will undertake in coming days is offloading the Fitzgerald’s weapons and fuel, and gathering data from the ship’s electronics so that the incident can be reconstructed. Presently, anyone going aboard the ship needs permission from a senior military officer.

Thomas Gibbons-Neff contributed to this report.

This story has been corrected to accurately define the USS Samuel B. Roberts incident.